Polyoxyalkylene block copolymers are well known to those skilled in the non-ionic surfactant art. Specifically, U.S. Pat. No. 3,740,421 (Schmolka) assigned to BASF discloses aqueous gels prepared using a block copolymer of polyoxyethylene/polyoxypropylene suitable for pharmaceutical and personal care compositions. U.S. Pat. No. 3,639,574 (Schmolka) assigned to BASF discloses polyoxyethylene/polyoxypropylene block copolymers as gelling agents for hydrogen peroxide compositions. U.S. Pat. No. 4,465,663 (Schmolka) assigned to BASF discloses polyoxybutylene/polyoxyethylene block copolymers as gelling agents for aqueous gels useful in personal care and pharmaceutical applications. Some of these compounds are sold by the BASF Corporation under the PLURONIC.RTM. tradename.
Additionally, U.S. Pat. No. 4,272,394 and U.S. Pat. No. 4,411,810 disclose the use of polyoxyalkylene block copolymers in machine dishwashing applications. U.S. Pat. No. 4,925,988 discloses a nonionic surfactant employing a specific combination of alkanol, ethylene oxide and propylene oxide useful in an automatic dishwashing application. U.S. Pat. No. 5,374,368 describes the use of liquid EO/PO/EO triblock co-polymers (PLURONIC.RTM. L 31 and L 35 surfactants) in stable hydrogen peroxide releasing dental care compositions at levels of 55-90% by weight of the dental care composition. U.S. Pat. No. 3,740,421 discloses gel forming solid EO/PO/EO triblock copolymers useful in cosmetic and personal care formulations at levels of approximately 20-25% by weight. Preferred solid EO/PO/EO triblock copolymers have a molecular weight of 4,600-16,000. Said solid EO/PO/EO triblock copolymers form a gel when added to an aqueous solution. U.S. Pat. No. 3,867,533 discloses aqueous gel compositions containing solid EO/PO/EO triblock copolymers, having a molecular weight of 6,450-20,000 useful at levels of approximately 20% by weight. Said compositions are useful in preparing cosmetic formulations. U.S. Pat. No. 4,465,663 discloses clear aqueous cosmetic gels containing solid EO/BO(butylene oxide)/EO triblock copolymers at levels of approximately 20%. U.S. Pat. No. 5,035,880 discloses a stable dentifrice compositions containing a cetylpyridinium bactericide and EO/PO/EO solid triblock copolymers (PLURONIC.RTM. F 127 surfactant), and polyethylene glycol at levels of 15-80% by weight. U.S. Pat. No. 4,476,107 discloses a mouthwash containing EO/BO(butylene oxide)/EO triblock copolymers at levels of 0.5-5.0% by weight. U.S. Pat. No. 5,057,307 discloses oral hygiene gels containing non-ionic surfactants, coating substances; and viscosifiers. Said non-ionic surfactants are PLURONIC.RTM. F 108 and F 127 surfactants available from BASF Corporation, Mt. Olive, N.J. U.S. Pat. No. 5,256,396 discloses a topical composition comprising an EO/PO/EO solid triblock copolymer (PLURONIC.RTM. F 127 surfactant) used at a level of more than 10% to about 17% by weight. EPO-546-627A discloses mouthwash compositions comprising solid EO/PO/EO triblock copolymers such as PLURONIC.RTM. F 108, F88 surfactants at levels of 0.5-3% by weight. U.S. Pat. No. 5,073,368 discloses mouthwashes containing solid EO/PO/EO triblock copolymers such as PLURONIC.RTM. F 87 surfactant at levels of 0.1-3% by weight. WO 93/13750 discloses an ocular cleansing composition comprising solid PLURONIC.RTM. F 87 and paste PLURONIC.RTM. P 85 EO/PO/EO triblock copolymers. PLURONIC.RTM. P 85 surfactant is 4-9% by weight of the cleansing composition, PLURONIC.RTM. F 87 surfactant is 0.5-2% by weight of the cleansing composition. Finally, U.S. Pat. No. 5,096,698 discloses a dental creme composition containing a non-ionic triblock liquid EO/PO/EO copolymer or a solid triblock EO/PO/EO copolymer at levels of 0.1-5% by weight. Said copolymers help to prevent phase separation. PLURONIC.RTM. F 108 surfactant (solid) is most preferred, followed by PLURONIC (.RTM. F 87, PLURONIC.RTM. ) F 127, and PLURONIC.RTM. ) L 72 surfactants. U.S. Pat. No. 4,272,394 discloses novel, low foaming nonionic surfactant for machine dishwashing compositions. U.S. Pat. No. 4, 411,810 discloses a low foaming, low cloud point, nonionic surfactant for machine dishwashing compositions. U.S. Pat. No. 5,496,542, U.S. Pat. No. 5,374,368, and U.S. Pat. No. 5,424,060 disclose the use of polyoxyalkylene compound for formulating a stable percarbonate formulation as well as a dentifrice composition. U.S. Pat. No. 5,187,191 discloses polyoxyalkylene heteric block surfactants in agricultural formulations. Finally, JP 47-48366 B4 discloses a process for producing tasteless, liquid, heteric polyoxyalkylene compounds of molecular weight 1000 or higher. However, a major problem with these polymeric materials is that they have high pour points (more close to ambient temperatures) which limits their use in processing cosmetic and toiletry compositions. Furthermore, the polymers of the JP 47-48366, B4 application develop a greater degree of crystallinity which manifest itself as haze and precipitated solids upon storage.
Applicants have surprisingly discovered a method for producing liquid, heteric-block polyoxyalkylene compounds with significantly lower pour points (i.e. more close to freezing temperatures) which substantially increases their utility in personal care compositions. Furthermore, the polymers of the Applicant's invention when neutralized with common inorganic acids result in compositions that are essentially clear and virtually free from precipitated solids during storage. Applicants have achieved this by selectively controlling the distribution or placement of propylene oxide and ethylene oxide in the polymers of the Applicant's invention. Without being limited by theory, the Applicants wish to stress that it is particularly important to control the distribution or placement of C.sub.3 or higher alkylene oxides in the polymer chain, in order to effectively minimize or eliminate the formation of crystalline segments in the polymer. When the formation of crystalline segments in the polymer is allowed to occur, said crystalline segments fall out of solution resulting in a undesirable two-phase product. The Applicant's approach to overcome this problem in the art differs from the method disclosed in the JP 47-48366 B4 application wherein the alkylene oxides are randomly distributed throughout the polymer chain. Such polymers as disclosed in JP 47-48366 B4 comprised solely of a random distribution of alkylene oxides throughout the polymer chain are outside the scope of the Applicant's invention.